Monster Girl Quest has several modes of Difficulty throughout the game, which generally makes all enemies harder to fight.
On higher difficulties, the enemies will generally have more HP, making the battle last longer. To turn the tables against the player, Status Ailments sometimes last longer as well, and Gnome may have difficulty breaking out of binds as well as Sylph and Undine having reduced rates of dodging an attack. In rare cases, the monster may use certain attacks not available in Normal, or may even keep fighting as opposed to their normal defeat.
Some monsters lack Hard or Hell difficulties, usually because the fight only has a simple scripted event.
The most basic difficulty of all. Monsters have moderate HP and damage and the Four Spirits do not falter on this difficulty. Normal difficulty is best for novice players.
In Hard difficulty, monsters are more difficult to defeat than Normal. In addition to having more HP and attack power and and the Four Spirits not working effectively, monsters such as Mandragora, Goblin Girl, Tiny Lamia, and Vampire Girl will keep fighting as opposed to being normally defeated on Normal mode due to a scripted event, allowing access to Monsterpedia technique entries. Hard difficulty is more suited for hardcore players.
Only available through the Monsterpedia, Hell mode is the hardest difficulty of all. It is a step up above Hard, as monsters will have even more HP and attack power and the Four Spirits have a higher rate of backfiring. Usually the battle is decided in the favor of the monster, but defeating an opponent in Hell difficult grants the achievement Won a Fight on HELL mode.
After completing all of Chapter 3 once, this mode is unlocked. EX difficulty allows the player to instantly defeat most monsters in one hit. However, in events where the battle leads to the player's defeat, such as the first fights of Alice and Tamamo, they will take damage normally. Despite the monster's instant loss in storyline scripted events where they actually lose because of something else, such as the first fight with Granberia, Alma Elma, Erubetie, Undine, and Salamander, the dialogue will continue as if the player never actually defeated them; for example Granberia's defeat results Alice immediately butting in, Alma Elma reacts as if she used her hands to catch Demon Skull Beheading, Erubetie reacts as if Undine blocked her attack, and Undine and Salamander immediately say Luka passed their test.